Friday, August 7, 2009

Researchers at the University of Liverpool have discovered that the Amazon river, and its transcontinental drainage, is around 11 million years old and took its present shape about 2.4 million years ago.

University of Liverpool researchers, in collaboration with the University of Amsterdam and Petrobras, the national oil company of Brazil, analysed sedimentary material taken from two boreholes near the mouth of the river to calculate the age of the Amazon river and the Amazon deep sea fan.

Prior to this study the exact age of the Amazon, one of the two largest rivers in the world, was not known. Until recently the Amazon Fan, a submarine sediment column around 10km thick, had proven difficult to penetrate. New exploration efforts by Petrobas, however, have lead to two new boreholes being drilled near the mouth of the Amazon - one 2.5miles (4.5km) below sea level - which resulted in new sedimentological and paleontological analysis of samples from the river sediment.

"River sediment records provide a unique insight into the palaeoclimate and geography of the hinterland," said Jorge Figueiredo from the University's Department of Earth and Ocean Sciences

"This new research has large implications for our understanding of South American paleogeography and the evolution of aquatic organisms in Amazonia and on the Atlantic coast. The origin of the Amazon river is a defining moment: a new ecosystem came into being at the same time as the uplifting Andes formed a geographic divide."

The study was published in the scientific journal, Geology, in July 2009.